Coliforms
Coliforms are the group of bacteria used by the water industry to assess the microbiological quality of water—both drinking water and recreational water.

These bacteria, though not generally pathogenic (disease-causing) themselves, serve as indicators of the presence of organisms which may be pathogenic. Coliforms, specifically fecal coliforms, indicate the possible presence of fecal contamination from warm-blooded animals.

While the standards for bathing beaches are not as stringent as those for drinking water, state or local authorities can prohibit swimming if bacterial levels are too high. Because fecal coliforms are associated with animal wastes, coliform levels tend to increase dramatically following storms as flood waters wash into rivers and lakes.

Research conducted at swimming-permissible beaches in Lake Mead has shown coliform levels within the established environmental safety standard.